JPH1187136A - Magnetic levitation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of a magnetic levitation system by exciting an electromagnet by using an AC power source having a variable voltage amplitude and adjusting the magnetic attracting force of the electromagnet by controlling the voltage impressed upon the electromagnet, and then, levitating a body provided with a magnetic body which is attracted by the magnetic attracting force from the electromagnet to a fixed position. SOLUTION: An electromagnet 1 which maintains a body in a levitated state is excited with an exciting current supplied to the winding 1a of the electromagnet 1 from an AC power source 3 having a variable voltage amplitude through a transformer 2 which plays the role of an impedance converter. The body is provided with a magnetic body 4 which is attracted by the magnetic attracting force from the magnetic poles of the electromagnet 1. Since the attracting force of the electromagnet 1 is proportional to the square of the exciting current, the force contains an AC component having a frequency which is twice as high as that of the AC power source 3 and DC component. Therefore, the body can be maintained in a levitated state with the DC component when the frequency of the power source 3 is made higher in such a degree that the AC component of the magnetic attracting force does not affect the movement of the magnetic body 4 by setting the frequency of the power source 3 to a frequency which is 10-20 times as high as that of commercial power supply and exciting the electromagnet 1 with the power source 3 having a variable voltage amplitude.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation system, and more particularly, to a magnetic levitation apparatus that uses a magnetic attraction of an electromagnet to levitate and hold a floating body having a magnetic material in a non-contact manner.

[0002]

2. Description of the Related Art In recent years, the above-mentioned magnetic levitation device has been widely used for a magnetic levitation transfer device, a magnetic bearing, a vibration isolator and the like. In such a magnetic levitation device, the electromagnet exerts a magnetic attraction force on the magnetic body of the levitated body, and levitates and holds the levitated body at the target levitating position in a non-contact manner. For controlling the levitation holding, a position sensor for detecting the levitation position of the levitation object and a controller for controlling the excitation current of the electromagnet based on the signal of the sensor are generally used.

That is, the actual floating position of the object to be levitated is detected by a position sensor, compared with a target floating position in the controller, and the difference is input to a compensation circuit. The compensation circuit reduces the difference. A compensation control signal is output, and the magnitude of the magnetic attraction force is increased or decreased by supplying an exciting current to the windings of the electromagnet in accordance with the control signal. Thus, the feedback control is performed so that the floating position of the floating object coincides with the target position.

However, the position sensor used in such a conventional magnetic levitation device is generally an expensive electronic device, and this is one of the causes of an increase in the cost of the magnetic levitation device. As a countermeasure, the following method without using a position sensor has been proposed.

(1) Observer method An observer is formed by using an exciting current of an electromagnet as an observation output, and the estimated position information of the magnetic body is fed back to a DC power supply of variable voltage amplitude to achieve stable magnetic levitation. (2) Signal superposition method When exciting an electromagnet with a DC power supply having a variable voltage amplitude, a high-frequency signal is superimposed on a voltage control command signal, and the position of the magnetic body is estimated from a high-frequency component of the resulting excitation current.

[0006]

However, both of the above-mentioned methods are based on the premise that the position of the magnetic material is estimated, and electronic equipment and a controller therefor are still required. The low cost benefits of halving are reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and achieves a stable magnetic levitation without estimating a levitation position, and can eliminate the need for a controller as well as a position sensor. The purpose is to provide.

[0008]

According to the magnetic levitation system of the present invention, an electromagnet is excited by using an AC power supply having a variable voltage amplitude, and the voltage applied to the electromagnet is controlled to thereby control the magnetic attraction of the electromagnet. Is adjusted so that the levitated body provided with the magnetic material exerting the magnetic attractive force is levitated to a predetermined position.

Further, the AC power supply detects a change in voltage and current on the load side, and changes the voltage amplitude of the AC power supply based on the detected change, thereby reducing the exciting current of the electromagnet. It is characterized in that it is adjusted and a floating body having the magnetic body is held at a fixed position.

According to the present invention described above, the DC magnetic attractive force is increased by using an AC power supply of variable voltage amplitude and increasing the frequency of the exciting current supplied to the windings of the electromagnet to a certain extent. Of the magnetic material. Then, by making the supply voltage of the AC power supply variable, the magnitude of the magnetic attraction force can be made variable. Thus, by detecting a change in the voltage and current on the load side as viewed from the AC power supply having a variable voltage amplitude, feedback control is performed such that the change is reduced to zero. It is possible to stably hold and float.

[0011]

FIG. 1 shows an embodiment of a magnetic levitation system according to the present invention. Electromagnet 1 for levitating and holding a floating object
Is an AC power supply 3 having a variable voltage amplitude via a transformer 2 serving as an impedance converter, and is excited by supplying an exciting current to its winding 1a. The levitated body includes a magnetic body 4 to which a magnetic attraction force is applied from the magnetic poles of the electromagnet 1. Since the magnetic attraction force of the electromagnet 1 is proportional to the square of the exciting current, an AC component and a DC component having a frequency twice as high as the frequency of the AC power supply 3 are included. Therefore, when the frequency of the AC power supply 3 is set to be 10 to 20 times the commercial frequency, the DC component of the magnetic attraction of the electromagnet 1 balances the gravity acting on the magnetic body 4 and the AC component reduces the inertia of the magnetic body 4. A negligible state can be realized by the effect. That is, the electromagnet 1 is excited by the AC power source 3 having a variable voltage amplitude, and the power supply frequency is set sufficiently high so that the AC component of the magnetic attraction force of the electromagnet does not affect the motion of the magnetic body. Levitation holding by the DC component.

FIG. 2 is an example of a circuit configuration of the AC power supply 3 of FIG. The variable voltage amplitude AC power supply 3 includes a sine wave oscillator 3a, a power amplitude unit 5 for amplifying a reference signal from the sine wave oscillator to a predetermined voltage amplitude, and a circuit for detecting changes in load voltage and current. And a signal amplifier 11 for feeding back the change. That is, a drive circuit is basically composed of the differential feedback power amplifier and the oscillator.

A reference signal is input to this circuit from its input terminal by a sine wave oscillator 3a having a frequency of 10 to 20 times the commercial frequency. The reference signal is amplified and output by the power amplifier 5, and supplies a reference exciting current to the winding 1a of the electromagnet 1 via the transformer 2 as a load. The reference excitation current generates a DC magnetic attraction necessary to keep the levitated body provided with the magnetic body 4 at the reference position.

This current flows from the terminal O ₁ to the primary side of the transformer 2, returns to the power supply circuit, and connects the output terminal O ₂ to the resistor 7.
Through to the ground line. Thus from the voltage dividing resistors 6 connected between the output terminal O ₁ and the ground line, when the resistance value is sufficiently higher than the load, the voltage signal at the output terminal O _1, i.e. the load voltage The signal can be extracted. On the other hand, the resistor 7 connected between the output terminal O ₂ and the ground line
Is, if this resistance value is low enough for the load side,
A current signal of the reference excitation current, that is, a current signal of the load can be extracted.

A voltage signal detected at a dividing point of the resistor 6;
The current signal of the resistor 7 is processed by the signal amplifier 9 and the phase shifters 8 and 10 so as to generate a difference between their amplitudes when the magnetic body is shifted from the reference position. That is, the amplitude and the phase of the voltage detection signal and the current detection signal are matched by the phase shifter 8, the signal amplifier 9 and the phase shifter 10 so that the magnetic body 4 is at the reference position, that is, the addition result of the adder 11a is obtained. It is adjusted in advance to be 0. Therefore, when the magnetic body 4 is at the reference position, the output of the signal amplifier 11 is zero. On the other hand, when the magnetic body 4 deviates from the reference position, the impedance of the electromagnet 1 changes, so that the balance between the voltage detection signal and the current detection signal is lost, and a difference signal is generated at the output of the signal amplifier 11.

This difference signal is converted into a feedback correction signal by the phase shifter 12 and the band-pass filter 13,
The signal is input to the adder 5a on the input side of the current amplifier 5 together with the reference signal. That is, when both the load voltage and the load current change, a change in the magnetic attraction force of the electromagnet 1 for returning the magnetic body 4 to the reference position is generated. The strength of such feedback correction is determined by the gain of the signal amplifier 11. In addition, such amplification, phase adjustment, and filtering of the difference signal produces not only a restoring force for returning the magnetic body to the original reference position, but also a damping effect for suppressing a position change of the magnetic body. As a result, stable magnetic levitation can be achieved with only a variable amplitude voltage AC power supply using a differential feedback power amplifier.

Further, the damping characteristic in the correction operation depends on the phase-frequency characteristic of the phase shifter 12. Further, the stability of such a differential feedback system depends on the gain-frequency characteristics of the band-pass filter 13. Therefore, a more stable and robust magnetic levitation system can be constructed by appropriately adjusting the electrical characteristics of these circuit elements.

Further, a signal amplifier used for the power supply,
Since the phase shifter, band-pass filter, and power amplifier can all be realized by general-purpose operational amplifiers, cost reduction of the magnetic levitation device can be further promoted.

It should be noted that the power supply circuit of variable amplitude voltage shown in the above-described embodiment shows only one configuration example, and it is needless to say that various modifications can be made without departing from the gist of the present invention. is there.

[0020]

As described above, according to the magnetic levitation system of the present invention, a magnetic levitation system using a magnetic attraction force only with an AC power supply having a variable voltage amplitude without using a controller as well as a position sensor. Can be constructed. For this reason, a magnetic levitation device that is less expensive in a field requiring magnetic levitation technology can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of a magnetic levitation device of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the AC power supply circuit in FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electromagnet 2 impedance conversion transformer 3 variable amplitude AC power supply 4 magnetic material 5 differential input type current amplifier 6 voltage detection resistor 7 current detection resistor 8, 10, 12 phaser 9 signal amplifier 11 differential input type signal amplifier 13 Bandpass filter

Claims (2)

[Claims] An electromagnet is excited by using an AC power supply having a variable voltage amplitude, and a voltage applied to the electromagnet is controlled to adjust a magnetic attraction force of the electromagnet to exert the magnetic attraction force. A magnetic levitation method characterized in that a levitated body having a magnetic body is levitated to a fixed position. 2. The AC power supply detects a change in voltage and current on the load side, and changes the voltage amplitude of the AC power supply based on the detected change, thereby reducing the excitation current of the electromagnet. 2. The magnetic levitation system according to claim 1, wherein the levitation body is adjusted and held at a fixed position.